A latest video encoding method, such as MPEG-4 AVC/H.264 (non patent literature (NPL) 1) and a future generation high-efficiency video coding (HEVC), supports the inter-picture prediction utilizing motion compensated prediction from more than one reference picture.
Recent advancements, such as ongoing development of an HEVC video coding standard, may utilize a hierarchical coding structure in design, experiment, and evaluation activities. Advantages of the hierarchical coding structure include improved coding efficiency and improved picture quality. In the hierarchical coding structure, pictures are arranged in temporal levels where the lowest level represents a lowest frame rate and inclusion of subsequent high levels (the temporal level is 1 or 2) represents higher frame rates.
The temporal levels are also used for enabling a feature of temporal scalability of a coded video bitstream. Switching from a higher temporal level (higher frame rate) to a lower temporal level (lower frame rate) is enabled by restricting picture referencing so that a current picture only refers to reference pictures at the same or lower temporal levels. On the other hand, switching from the lower temporal level to the higher temporal level is enabled by using a temporal nesting scheme. However, when a picture having a lower temporal level is decoded in a coding order, reference pictures having higher temporal levels can no longer be used for prediction.